1. Field of the Invention
The present invention relates to a fuel supply system for internal-combustion engine and, more particularly, to a fuel supply system for internal-combustion engine arranged such that a richer air-fuel mixture is supplied to the vicinity of an ignition plug in a combustion chamber defined by a cylinder and a piston.
2. Description of the Prior Art
It has been generally known that operating internal-combustion engines on a lean air-fuel mixture is effective in reducing the fuel consumption as well as the amount of noxious components in the exhaust gas.
Such internal-combustion engines employing a lean air-fuel mixture require making the air-fuel mixture in the vicinity o the ignition plug richer than that surrounding the same in order to ensure the ignitability of the air-fuel mixture.
Therefore, in, for example, U.S. Pat. No. 3,842,810 a method has been proposed in which an auxiliary combustion chamber is formed separately from a main combustion chamber defined by a cylinder and a piston, and a rich air-fuel mixture is supplied to the auxiliary combustion chamber and ignited by means of an ignition plug, and then the flames of the rich air-fuel mixture are propagated to ignite a lean air-fuel mixture in the main combustion chamber.
Such a method, however, disadvantageously requires additional provision of both an auxiliary combustion chamber and an air-fuel mixture supply means for supplying a rich air-fuel mixture thereto.